Space tests of relativistic gravity with precision clocks and atom interferometers

Precision clocks and interferometers in space can test relativistic gravity with extremely high sensitivity. Yet, only a single such test has been performed, namely the celebrated flight of a hydrogen maser in a sub-orbital trajectory in 1976 (GP-A mission). This paper suggests some of the obstacles to space flight of precision instruments, and describes how the emergence of new technology might offer a pathway for removing those obstacles. A brief review of emerging technologies is made, and new mission concepts based on them are described. Some of the technologies that can impact more tests of relativistic gravity in space at a more distant future are also described.     

Spin–gravity coupling and gravity-induced quantum phases

External gravitational fields induce phase factors in the wave functions of particles. The phases are exact to first order in the background gravitational field, are manifestly covariant and gauge invariant and provide a useful tool for the study of spin–gravity coupling and of the optics of particles in gravitational or inertial fields. We discuss the role that spin–gravity coupling plays in particular problems.     

Energy Distributions of the Szekeres Universes in Teleparallel Gravity

In order to evaluate the energy distribution (due to matter and fields including gravitation) associated with a space-time model of Szekeres class I and II metrics, we consider the Einstein, Bergmann–Thomson and Landau–Lifshitz energy definitions in the teleparallel gravity (the tetrad theory of gravitation (TG)). We have found that Einstein and Bergmann–Thomson energy distributions give the same results, Landau–Lifshitz distribution is disagree in TG with these definitions. These results are the same as a previous works of Aygün et al., they investigated the same problem by using Einstein, Bergmann–Thomson, Landau–Lifshitz (LL) and Møller energy-momentum complexes in GR. However, both GR and TG are equivalent theories that is the energy densities are the same using different energy-momentum complexes in both theories. Also, our results are support the Cooperstock’s hypothesis.     

利用Adobe Audition 1.5测重力加速度

介绍了利用声学处理软件Adobe Audition 1.5 记录小球自由落体运动的时间,再通过直线运动公式计算重力加速度的方法.该方法可以将运动时间精确到0.001 s, 从而能够更精确地计算出重力加速度.     

冲击压裂缩尺混凝土试件室内实验研究

通过对缩尺混凝土板体在冲击荷载作用下的破坏行为进行研究分析,实现对室外冲击的模拟。试验以几何相似为准则,采用类落锤装置提供冲击荷载,通过控制落锤冲击次数,对缩尺板体进行固定位置的冲击破坏,并运用动态观测技术对试件上不同测试点进行观测,以达到研究板体破坏特性的目的。实验表明,冲击压裂合适尺寸的缩尺混凝土板体能够很好地模拟冲击破碎情况;在板体未破坏之前,测试点最大应变响应值与冲击次数呈现出线性的增长;当板体区域刚开始发生结构变化时,变化区的测试点应变响应就会达到其测试峰值;板角,板边和板中对角线上的测试点的应变响应增减量变化与测试区域的破坏状态有关。     

泥石流拦砂坝排泄孔优化及其数值模拟研究

为改善拦砂坝排水孔堵塞问题,提出了以调节泥石流流量为主的排水孔优化策略;并通过数值模拟初步研究了横、纵断面形态对优化后的排水孔(排泄孔)排泄能力的影响,以及排泄孔对不同性质的泥石流的排泄效果。通过对横断面形态、纵断面形态及浆体容重三因子的正交组合,进行了80组模拟试验,以平均排泄流量珚Q和坝前泥深下降速率为主要评价指标,结果表明具有合理宽深比的矩形横断面相对最优。对容重较小的流体,窄深型的矩形断面排泄能力最好;而对高容重流体,则正方形断面相对更好。在可流动范围内,排泄效果随着排泄孔纵比降的增大而增大;而增大沿程排泄孔横断面截面积(变截面一坡到底喇叭型)可提高相同纵比降排泄孔的排泄能力。同时,随着流体容重的增加,排泄孔的排泄能力逐渐降低。     

机制砂混凝土的冻融和盐侵蚀耐久性

对机制砂混凝土进行了冻融循环试验。考虑了三种强度等级(C30、C40、C50)和四种介质(清水、质量分数为5%的氯化钠溶液、质量分数为5%的硫酸钠溶液和5%氯化钠溶液+5%硫酸钠溶液组成的混合盐溶液)。重点考察质量损失率、相对动弹性模量和抗压强度的变化。结果表明:随着冻融循环次数的增加,四种环境下机制砂混凝土的质量、相对动弹性模量和抗压强度均呈下降趋势;盐的存在加剧了机制砂混凝土在冻融循环过程中产生的表层剥落,却减缓了机制砂混凝土相对动弹性模量的下降;盐溶液种类对机制砂混凝土冻融后质量损失率和相对动弹性模量的影响程度不同,氯化钠比硫酸钠的破坏力强。     

超长混凝土框架早期温度应力公式的修正

以一超长混凝土框架结构实例为基础,采用有限元分析软件ANSYS对影响结构温度应力的四种主要影响因素(结构长度、柱子刚度、梁刚度、柱间跨度)进行分析,利用粘弹性理论做正交试验极差分析.依据正交试验基本原理建立与之对应的九个ANSYS模型,基于正交实验的结果对已有温度应力的公式做一定的修改,具有一定的实际指导意义.